1. Field of the Invention
This invention relates to a color image communication apparatus and method.
2. Related Background Art
Heretofore, when color data is converted to monochrome data, for instance when RGB data is converted to luminance data Y, the data length is changed, and subsequently the same processing circuit can not be used. Therefore, it is necessary to separately provide a processing circuit for color and one for monochrome.
Specifically, considering a case when 8-bit serial data for each of R, G and B flows through the circuit, while color data processing is performed in synchronism to a sync signal for every 24 bits, after conversion of data to 8-bit data Y it is necessary to effect synchronization for every 8 bits. Alternation of the circuit is also necessary.
Further, for printing received RGB data of a color image, for instance, in the prior art color image communication apparatus a color masking processing is performed with respect to color characteristics of a color printer, and printing is done after color correction.
In such case, if monochrome data expressed in transmission format YOO or YYY (Y being luminanee data here) is received instead of RGB data, perfect black can not be obtained but a color-blended image is provided after color masking processing similar to the case of a color image.
These problems occur not only in connection with the color mode and monochrome mode but also in connection with the color mode and a single color mode, in which only single color data is transmitted.
Since color data and monochrome data are compressed in different ways, it is impossible to transmit data from a color facsimile apparatus to a G4 or like monochrome facsimile apparatus, for which an advice has already been given.
Accordingly, an apparatus has been proposed, in which data compression conforming to, for instance, G4 standards is performed on color image data read out from an original when it is intended to transmit the color image from a color facsimile apparatus to a G4 receiver.
Further, it may be thought that in the case of a monochrome original image a color facsimile apparatus transmits only monochrome image data after compression in conformity to the G4 standards without transmitting color image data.
However, when the receiver is a color facsimile apparatus, it is preferable in view of data transfer efficiency to use data compression having a higher compression factor instead of the standard compression method in case of a monochrome original image as well.